The semiconductor integrated circuit (IC) industry has experienced rapid growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. In the development of new MOS (metal-oxide-semiconductor) technologies, as well as the development of three-dimensional designs such as a fin field-effect transistor (FinFET), a key aim is to improve the mobility in the channel of the device. To achieve this, the use of materials with an improved mobility when compared to silicon has been considered, for example using materials such as germanium (Ge), gallium arsenide (GaAs), or silicon germanium (SiGe) with or without additional strain. There is also a desire to allow the control of the leakage current across the channel of the device.
For example, in order to produce a SiGe device, a full sheet epitaxy of SiGe is generally formed on a silicon substrate. However, this technique results in a SiGe layer which is too thick, and thus is not compatible with thin body devices. Also, the thicker the SiGe channel, the higher the leakage current. Therefore, there is a need for forming a SiGe channel sufficiently thin to achieve the requirement of low leakage current.